Helion, the nuclear fusion startup backed by Sam Altman, announced the completion of a $465 million Series G funding round, valuing the company at $15.5 billion. With this funding, Helion is accelerating construction of its first power plant, Orion, and attempting to fulfill its power supply agreement with Microsoft, aiming for grid connection as early as 2028.
Valuation rises to $15.5 billion
This funding round was led by Thrive Capital, with new investors including Alta Park Capital, Anti Fund, BoxGroup, Lux Capital, Peak XV Partners, and Bill Ford. Existing investors, including Capr Technology Impact Funds, Lightspeed Venture Partners, Mithril Capital, Good Ventures Foundation, SoftBank Vision Fund II, and a university endowment fund, continued to participate.
Helion stated that its total funding has reached $1.5 billion. Its last funding round was in January 2025, when it raised $425 million.
- This funding round: $465 million
- Latest valuation: US$15.5 billion
- Total funding: $1.5 billion
The first power plant is targeting a Microsoft contract.
This funding will be used to advance Project Orion. Helion is attempting to build its first commercial power plant and is pushing forward with a more aggressive timeline for nuclear fusion power generation. According to the company's current goals, if the terms of its partnership with Microsoft are fulfilled as planned, grid connection could be achieved as early as 2028.
Nuclear fusion has long been considered a high-density, sustainable potential energy source. For AI companies, a stable and continuous power supply is becoming increasingly important. With the expansion of data centers and the rising demand for model training, technology companies are also showing growing interest in new energy solutions.
Technical approach and skepticism coexist
Unlike many of its peers, Helion does not intend to rely primarily on steam turbines to convert thermal energy into electricity. The company uses magnets to compress fuel and plans to extract electricity directly from changes in the magnetic field after fusion occurs.
If feasible, this plan could theoretically improve power plant efficiency. However, significant external skepticism exists. The report notes that unlike many fusion companies, Helion does not frequently publish research in peer-reviewed journals, making it difficult for the external physics community to systematically verify its theoretical foundation. Helion CEO David Kirtley previously stated that the company prefers to use device results to prove its approach rather than remaining at the level of theoretical discussion.
Funding for fusion-related projects continues to heat up.
Despite the generally long commercialization cycle, the nuclear fusion field continues to attract investment. Last week, Focused Energy and Thea Energy announced the completion of $240 million and $100 million in funding, respectively. In February, Inertia Energy emerged from secrecy and disclosed a $450 million Series A funding round; earlier, Type One Energy also announced it was working on a $250 million Series B funding round.
Most fusion companies expect the first commercial-scale power plants to be operational no earlier than the middle of the next decade. Even so, capital markets are still betting on its long-term value: if nuclear fusion can reduce costs and provide a stable output of electricity, it could not only meet the needs of AI infrastructure but also reshape the broader energy market.
